The present invention disclosed herein relates to a micro device using Micro Electro Mechanical Systems (MEMS) technology, and more particularly, to a condenser-type acoustic sensor and a method of manufacturing the same.
An acoustic sensor (or a microphone) is a device converting an audio into an electrical signal. As developments of micro wire/wireless devices are accelerated recently, a size of the acoustic sensor becomes more miniaturized. Accordingly, the latest acoustic sensor using MEMS is developed.
The acoustic sensor is largely classified into a piezo-type and a condenser-type. The piezo-type uses piezo effect (a potential difference occurs at both ends of a piezoelectric material when physical pressure is applied to the piezoelectric material) and converts the pressure of an audio signal into an electrical signal. The piezo-type has many limitations in applications due to low band and irregular characteristics of audio band frequencies. The condenser-type uses a principle of a condenser having two facing electrodes in which one electrode of an acoustic sensor is fixed and the other electrode serves as a diaphragm. This is, if the diaphragm vibrates according to a pressure of an audio signal, an accumulated charge between the electrodes is changed because a capacitance therebetween is changed and thus current flows. The condense-type has advantages such as stability and excellent frequency characteristic. Due to the frequency characteristic, the acoustic sensor may typically use the conductive-type device.